Flexible and expansible band



Sept. 5, 1950 G. G. BERGH FLEXIBLE AND EXPANSIBLE BAND Filed May 1, 1948Patented Sept. 5, 1950 FLEXIBLE AND EXPANSIBLE BAND George G. Bergh,Attleboro Falls, Mass, assignor to Bergh Bros. 00., Inc., AttleboroFalls, Mass, a corporation of Massachusetts Application May 1, 1948,Serial No. 24,511

8 Claims.

. 1 1 This invention relates to flexible and expansilole bands and moreparticularly to expansible metallic straps, bracelets, necklaces, orsimilar bands used in supporting ornaments, and deriv- 'ing springtension from the coiled walls of the of each strip lie alongside eachother with edges contiguous and with the center of the outer strip lyingdirectly outside the contiguous edges of the inner strip. In the fullyexpanded position, the turns or wrappings separate but the out-turnededges of the inner strip and the in-turned edges of the outer stripinterlock preventing further expansion and separation.

The amount of expansion provided by the above described conventionalconstruction often is not suflicient to accommodate a person with alarge hand and still fit snugly to his wrist. Also, in case it isdesired to fit a necklace over the head of a person, the expansionafforded by the conventional band is not sufiicient to allow it to fitclosely around the neck and also pass over the head.

In attempting, however, to increase the ratio of expansion tocross-sectional area, one is restricted by certain physical limitationswith the conventional construction. That is, the width of the stripscontrols the expansib'iiity, but if the strips are widened withoutincreasing the crosssectional area, first, the spring tension of theband is increased rendering expansion more difficult, and second, sincethe cross-sectional area is not increased, the strips must be wrapped atgreater slanting angles. This latter .fact operates against effectiveexpansion by increasing the amount of cross-sectional contraction perunitof longitudinal expansion thus reducing the benefit of-the increasedwidth. Furthermore, since the inner strip is of necessity shorter thanthe outer strip, its cross-sectional area contracts more than that ofthe outer strip whenthe band is ex- "panded. This fact is morepronounced at greater angles of slant, rendering it more diilicult whenthe angle of slant is increased to attain effective locking of thein-turned and out-turned edges at the point of full expansion.

Accordingly, an object of my invention is to provide a constructionwhich is effective for intioned above.

ar-easing the ratio of expansion to cross-sectional area of a bandwithout increasing the width of the strips and without increasing theangle of slant at which the strips are wrapped.

in order to accomplish this object, I employ an inner strip with itsedges notched forming teeth the ends of which are bent outwardly.Outside and around the inner strip, I wrap an outer strip with inturnededge flanges. In the contracted state, the teeth of the inner stripintermesh and the flanges of the outer stripcome flush up against eachother, while in the fully expanded state, the strips may separate untilthe outwardly bent teeth on the inner strip interlock with the inturnedflange of the outer strip. Th-us, the width of the outer strip has notbeen increased, the same angle of slant has been maintained, but due tthe intermeshing of the teeth, the inside strip can be made wider andthe band is capable of greater expansion.

A further feature of my invention is the provision of notches in theinner strip substantially wider than the teeth formed by the saidnotches. This feature insures free access of the teeth into the notcheswhen the band is in the contracted state and is advantageous because theturns-oi the band do not separate at right angles to each other when theband is expanded.

An additional feature of my invention is the provision of a crimp in theside walls of the band when it is formed rectangular or parallelepipedshape. This feature insures interlocking of the outwardly bent tips ofthe teeth of the inner strip and the inturned edges of the outer stripwhen the band is expanded, and minimizes the effect of the greatercontraction of the inner strip men- This feature also serves to decreasethe length of the outer strip, fitting it more closely to the innerstrip.

These and other features of the invention will be best understood andappreciated from the vfollowing description of a preferred embodimentthereof, selected for purposes of illustration and shown in theaccompanying drawings, in which:

Fig. l is a view in perspective of a section of the band with the outerstrip in part cut away in order to show the inner strip and on a greatlyenlarged scale,

Fig. 2 is a view in side elevation with the outer strip cut away, andshowing in detail the intermeshing of the teeth in the inner strip,

Fig. 3 is a view in side elevation showing the inner strip fullyexpanded, and

inner strip partially expanded. V

In the preferred embodiment of my invention, I employ an inner metallicstrip ID in the edges of which are cut notches H, leaving teeth II, thesaid notches I I being substantially wider than the teeth I2 as is shownin Fig. 2. The outer ends of the teeth l2 are bent outwardly formingflanges, but it is to be noted that the notches II continue inwardtoward the center of the strip II! from the line on which the teeth I2are bent outwardly.

The inner strip I is wound helically in turns or wrappings ofrectangular form with the sides of such length as to permit the teeth I2of the adjacent edges to intermesh upon winding as shown in Fig. 1.

Outside and wound helically into the same form as the inner strip I0, isa metallic outer strip M which encloses the helix of the inner strip 10.The outer strip [4 serves the purpose of ornamentation and therefore maybe made of precious or polished metal. The edges of the outer strip Mare bent inward forming the flanges I5. Including the flanges l5, thewidth of the outer strip l4 equals the distance between the outerextremities of the teeth l2 in one edge of the inner strip l0 measuredacross to the base of the notches l I in the other edge of the innerstrip ID, as designated by the line in Fig. 4.

From this it can readily be seen that by notching and intermeshing theinner strip In its overall width including the teeth 12 in both edgescan be made substantially greater than the width of the outer strip l4and still maintain the same number of winds per inch. And, it furtherfollows that the greater the depth of the notches for a given number ofwinds per inch, the greater will be the amount of expansion.

The device of my invention is shown in two extreme conditions, one inwhich it is fully contracted (see Figs. 1 and 2), and the other in whichit is fully expanded (see Fig. 3). In the fully contracted position, theflanged edges of the outer strip 14 come flush up against each other andthe teeth l2 of the inner strip l0 intermesh. In the fully expandedposition, the teeth I2 of the inner strip 10, by means of theirout-turned ends, engage the flanges l5 of the outer strip M.

It will be apparent that inner strip H! may be wound as a helix upon arectangular or other shaped mandrel and then the outer strip 14 may bewound upon formed inner strip while the latter is still supported in itsmandrel. A crimped depression may be swaged into each turn of the outerstrip adjacent the vertices of each turn thus locally widening the stripand providing a slight clearance between its side edges as shown inFig. 1. This feature of construction results in increased flexibility ofthe band as a whole.

Inasmuch as the strips l0 and M are made of substantially resilientmetal, the band will tend to remain in the fully contracted position, ifwound initially in that position. However, since variations in windingor otherwise will readily suggest themselves to those skilled in theart, it

is not intended to limit the invention to the pre- 7 ciseembodimentherein described, but rather to confine it to the scope of the appendedclaims. Therefore, having thus disclosed my invention and described indetail an illustrative embodiment its edges so constructed and arrangedas to inter mesh when its edges lie contiguous in the helix, inturnedmarginal flanges on the outer said strip and out-turned flanges at theextremity of the said teeth on the inner said strip, the said flangesconstructed and arranged to meet when the strips are pulled apart.

2. A flexible and expansible band comprising an outer strip of flexiblemetal, an inner strip of flexible metal, an inturned flange on eachmargin of the said outer strip, each margin of said inner strip beingnotched to form spaced teeth and notches, an out-turned flange at theextremity of each of the said teeth, the said inner strip beinghelically wound and so constructed and arranged that when its oppositemargins lie relatively adjacent in the helix, the teeth of one marginflt into the notches of the adjacent margin, and the outer strip beinghelically wound about the inner strip in close proximity thereto withits margins meeting flush against each other when in contractedposition, and its inturned flanges lying between the out-turned flangesof the said teeth whereby contact between the said flanges will be madewhen the band is expanded thereby limiting further expansion.

3. A flexible and expansible band of the character described in claim 2,further characterized by the notches being wider than the teeth thusensuring unobstructed intermeshing when in the contracted position.

4. A flexible and expansible band of the character described in claim 3,further characterized by the said strips being pressed into rectangularform, and the said outer strip being crimped adjacent to each foldvertex in order to insure contact between the inturned and 0utturnedflanges.

5. A flexible and expansible band for ornamental purposes comprising aninner strip having teeth of uniform size and shape in its edges bentoutward at their extremities and spaced unlformly along the edges of thesaid inner strip at intervals substantially greater than the width ofthe said teeth, the said inner strip being helically wound such that theteeth of one margin thereof will flt in the spaces between the teeth ofthe contiguous edge when the band is contracted, and an outer striphaving an inturned flange on each margin thereof, the outer strip beinghelically wound around the said inner strip in close proximity theretowith its margins meeting flush against each other when in contractedposition, and its inturned flanges lying between the outturned flangesof the said teeth whereby contact between the said flanges will be madewhen the band is expanded thereby limiting further expansion.

6. A flexible and expansible band of the character described in claim 5,further characterized by the outer band having a width equal to thewidth of the adjacent inner band measured between the extremities of theteeth on one edge and the base of the space between the teeth on theother edge 7. A flexible and expansible band of the character describedin claim 6, further characterized by the strips being composed ofresilient metal,

and having parallel edges.

8. A flexible and expansible band for ornamental purposes comprising aninner strip of flexible metal, the said inner strip having uniformrectangular notches cut in its edges at equal intervals along its saidedges, teeth formed by the notches, the saidteeth being of less widththan the said notches and being bent at their extremities so as to formupstanding flanges, an outer strip of flexible metal with its edges bentso as to form depending flanges, the width of the outer strip andflanges being equal to the distance measured on the inner strip betweenthe base of the notches on one side and the extremity of the out-turnedteeth on the other side, the said strips being helicaliy wound withtheir edges overlapping and bent into rectangular shape.

GEORGE G. BERGH.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number Number 6 UNITED STATES PATENTS Name Date Armstrong July 25, 1911Eklund Sept. 24, 1918 FOREIGN PATENTS Country Date Germany July 2'7,1930

